A thin Film Bulk Acoustic Resonator (FBAR) is a technology that creates a frequency shaping element found in many modern wireless systems. When an alternating electrical potential is applied across the FBAR, a layer within the FBAR expands and contracts, creating a vibration. The vibrating membrane creates a high Q mechanical resonance. An FBAR may thus be used for a filter, duplexer, resonator, or the like.
It is, however, difficult to manufacture FBARs to the rigorous standards required by industry. Minute variations in the thickness of the layers which comprise the FBARs may result in unacceptable deviations in the operating frequency of the FBAR, resulting in an unacceptable product.
One technique to address the concern of manufacturing variations has been pioneered by Nokia and is explained in U.S. Pat. No. 6,051,907, which is hereby incorporated by reference in its entirety. While the techniques described in this patent are adequate, commercial need dictates that alternate approaches be made available for increased competitive opportunities.